A gas-filled tube, also known as a discharge tube, is an arrangement of electrodes within an insulating and temperature-resistant envelope that is gas filled. The electrodes, for example, include at least one negative electrode and at least one positive electrode. Sometimes, the electrodes alternate to act as the negative electrode (hereinafter referred to as ‘cathode’) and the positive electrode (hereinafter referred to as ‘anode’). The gas-filled tube exploits an electric discharge phenomenon in gases, and operates by ionizing the gas with an electric field. The ionized gas is typically referred to as plasma. The ionized gas generally contains charged particles including electrons, positive ions, and/or negative ions. The gas-filled tube, for example, is a plasma switch or a plasma lamp.
Typically, the ionization of the gas is initiated by introducing charged particles into the envelope, for example by irradiating an ionizing radiation in the envelope. The charged particles, for example include free electrons, positive ions, and/or negative ions. The positive ions drift towards the cathode, while the free electrons drift towards the anode. While drifting towards the anode, the free electrons collide with neutral gas molecules of the gas. If the electric field applied to the gas-filled tube is strong enough, the free electrons gain sufficient energy to further liberate electrons during the collision of the free electrons with the neutral gas molecules. The liberated electrons and the free electrons then travel towards the anode and gain sufficient energy from the electric field to cause impact ionization when further collisions of the liberated electrons and free electrons occur with the neutral gas molecules; and the process of ionization continues. The liberated electrons are typically referred to as ‘secondary electrons’. Furthermore, the ionized gas is typically referred to as ‘plasma’. Generally, the secondary electrons yield is a function of an energy of an electron (secondary electron or free electron) colliding with a neutral gas atom and/or molecule. Furthermore, secondary electrons may also be generated by ions (heavy particles) with the cathode.
Typically, gas-filled tubes are based on hydrogen plasmas. In operation, the gas filled in the gas-filled tubes is typically hydrogen. Generally, the secondary electrons emitted as a function of an energy of an electron (liberated electron or free electron) colliding with a neutral gas molecule for such hydrogen plasmas is less than secondary electrons emitted as a function of energy of an electron colliding with a neutral gas molecule for helium plasmas, for example. Furthermore, in the gas-filled tubes filled with hydrogen (hereinafter referred to as ‘hydrogen gas filled tubes’), only about one-third of electric power supplied to the hydrogen gas-filled tubes is used for the process of ionization, and the rest of the electric power is used for other atomic processes associated with hydrogen. Accordingly, the rate of ionization as a function of the electric power supplied to the hydrogen gas-filled tubes is less than the rate of ionization as a function of the electric power in helium gas-filled tubes, for example.
Usage of helium gas in the gas-filled tubes (hereinafter referred to as ‘helium gas-filled tubes’) leads to better secondary electron yield as a function of energy of an electron (liberated electron or free electron) than usage of the gas hydrogen. Furthermore, usage of helium in the gas-filled tubes leads to a better rate of ionization as a function of the electric power supplied to the hydrogen gas-filled tubes. However, regulation and control of pressure of helium in the helium gas-filled tubes is a challenge. Furthermore, typically large helium vessels are available and used for regulation and control of pressure of helium in the helium gas-filled tube.
Accordingly, helium reservoirs for supplying helium to gas-filled tubes are required. Furthermore, helium reservoirs for regulating and controlling the pressure of helium in the gas-filled tubes are required.